1. Field of the Invention
The present invention relates to a device having a bayonet ring that is attachable and detachable via a bayonet mechanism and to a camera typifying such a device.
2. Description of the Related Art
Conventionally, a bayonet mechanism has been widely used as a mechanism for freely attaching and detaching a ring-shaped member to and from a camera body. The bayonet mechanism includes: an arc-shaped groove and a fixed hook formed on and protruding from the arc-shaped groove, which are provided in a camera body; and an arc-shaped projection and a stop hook, which are provided in a ring-shaped member. The arc-shaped projection is to be engaged in the arc-shaped groove, and the stop hook is to go under the fixed hook and stopped by it when the arc-shaped projection is engaged in the arc-shaped groove and rotated.
For example, Japanese Patent Application Publication No. 1-159624 discloses a thin bayonet ring having elastic portions.
The bayonet ring disclosed in Japanese Patent Application Publication No. 1-159624 needs a force to bend the elastic portions at the time of attachment or detachment of the bayonet ring, and a user holds the side of the bayonet ring to operate it. Bayonet rings are usually operated in this way.
Recently, with the growth of the demand for thinner cameras, the demand for thinner bayonet rings is also growing. However, as for the case of the bayonet ring disclosed in Japanese Patent Application Publication No. 1-159624, it is difficult to make the bayonet ring thinner because the side of the bayonet ring needs to be held when it is operated. A bayonet ring whose side is not thick enough to be held may be conceived. A user needs to operate such a bayonet ring by holding the front face thereof with the fingers. The user can only push and rotate the top (front face) of the bayonet ring when attaching the bayonet ring to a camera body, and also can only push and rotate the top of the bayonet ring in a detachment direction when detaching it. However, there arises a problem of how to remove the bayonet ring from the camera body after it is rotated up to a detachment position.
For example, it is conceivable that the bayonet ring may be dropped by tapping the camera body while holding it with the front face facing downward. However, tapping the camera body is not desirable because a camera is delicate equipment. Moreover, the dropped bayonet ring may be damaged or the camera body itself may be dropped and damaged as well.
Alternatively, it is conceivable that the bayonet ring may be urged by a spring having a force to lift up the bayonet ring so that the bayonet ring can be automatically lifted up when it is rotated up to the detachment position. In this case however, a user needs to push the bayonet ring with a force strong enough to overcome the spring's force and needs to rotate it while pushing it when attaching the bayonet ring to the camera body, which requires techniques because the bayonet ring is unstable when placed on the camera body. Moreover, the fingers may be slipped from the front face of the bayonet ring because the user also needs to apply a force to rotate the bayonet ring, leading to low operability in attachment and detachment of the bayonet ring.